Figure 4
Emission spectra (λexc = 350 nm) of CdSe/CdS-QDs in the reaction mixture before the polymerization reaction and the resulting QD-encoded PS microbeads in ethanol, obtained for (a) OA/OLA-stabilized QDs, crosslinked with DVB, (b) OBDAC-coated, OA/OLA-stabilized QDs without crosslinking, with PEG-b-PCL, (c) for optimized conditions, i.e., OBDAC-coated, OA/OLA-stabilized QDs, addition of PEG-b-PCL, and crosslinking with DVB, and (d) the corresponding PLQY values obtained at different reaction stages and for the initial QDs. Conditions used for the preparation of the QD-encoded PS beads: 75 °C, 36.6 mg AIBN, 36.6 mg PEG-b-PCL, 70 rpm stirring speed, and 24 h reaction time. For the comparison of the PL spectra, the emission intensity of the QDs in the initial reaction mixture was always set to one and the other spectra were scaled accordingly. The observed shift of the emission maxima is attributed to the change in QD environment from initially styrene/ethanol to polystyrene after the polymerization reaction. The increase in PL intensity of the beads in panels (a,c) washed 5 times with ethanol compared to the PL of the beads after a reaction time of 24 h is attributed to a slight change in bead concentration and bead loss during the washing steps as revealed by the corresponding absorption spectra displayed in the SI (Fig. S4).
